So-called cyclones are used on a large scale to separate gas/liquid mixtures, for instance to dry natural gas. On extraction the natural gas can be mixed with salt water, which can cause much corrosion in the pipelines through which the gas must flow.
In a so-called axial cyclone the entering mixture is set into a rotating movement, whereby a heavy fraction (in the order of magnitude of 2–25% of the total flow) in which a relatively large amount of liquid is present, is flung against the outer wall of the cyclone. This fraction can be discharged by arranging openings in the outer wall. It is also already known to reintroduce a part of the discharged fraction into the liquid flow in order to further separate this fraction as well into liquid and gas phase.
In the known cyclones the outlet opening for the returned flow is usually arranged in the centre of the cyclone. As the mixture has a substantially axial speed component in the centre of the cyclone, creep may occur along the outlet opening whereby liquid droplets from the inlet flow enter the outlet flow. When capacity is increased, i.e. when the pressure and/or the quantity of the mixture is increased, such creep will become worse.
In view of the above, the capacity of such a cyclone forms a limitation, whereby installations for the desired gas/liquid separation would have to increase in size, which is undesirable.